In some embodiments, the present disclosure relates to a method for forming an image sensor and associated device structure. A backside deep trench isolation (BDTI) structure is formed in a substrate separating a plurality of pixel regions. The BDTI structure encloses a plurality of photodiodes and comprising a first BDTI component arranged at a crossroad of the plurality of pixel regions and a second BDTI component arranged at remaining peripheries of the plurality of pixel regions. The first BDTI component has a first depth from a backside of the substrate smaller than a second depth of the second BDTI component.